STRAIN-INDUCED DISORDERING OF METAL-SURFACES - RAPID LASER-HEATING OF RH(111) AND RH(332)

Laser-induced disordering of clean and adsorbate covered rhodium surfaces has been studied by LEED and by laser-induced thermal desorption (LITD) of deuterium. Excimer laser (308 nm) pulses with 120 ns duration and intensities between 35 and 85 MW cm-2 were applied, covering a regime commonly used in LITD studies. Rh{111} is more resistant to disordering than Rh{332}, a surface made up of six-atom-wide {111} terraces separated by monatomic steps, consistent with a decrease in the activation energy for disordering due to steps from 59 to 39 kJ mol-1. Onset temperatures for disordering are estimated as 954 K ({111}) and 700 K ({332}). No ''protective'' effect was found for adsorbate monolayers of oxygen and carbon monoxide. A simple stress-strain model provides an understanding of elastic and plastic deformation during short pulse laser heating and rapid cooling. Some guidelines for reducing damage in LITD experiments are given.